Automatic coupling mechanism for semitrailers



' June 7, 1932. H. w. HELMS AUTOMATIC COUPLING MECHANISM FOR SEMITRAILERS Filed May 51, 1930 5 Sheets- Sheet 1 lhyemioz. I. 1%? 5 fZi Wet/2275. 45 14521227? ys.

June 7, 1932. I H. w. HELMS 1,362,115

AUTOMATIC COUPLING MECHANISM FOR SEMITRAILERS Filed May 51, 1950 s Sheets-Sheet 2 June 7, 1932.

H. w. HELMS AUTOMATIC COUPLING MECHANISM FOR SEMITRAILERS 5 Sheets-Sheet s 5341f ofzzgya June 1932 H. w. HELMS AUTOMATIC COUPLING MECHANISM FOR SEMITRAILERS Filed ma 51, 1950 5 Sheets-Sheet 4 .Zfwfiezz Z02". rfz: W 322 5.. 15145 forzze g/s June 7, 1932. H. w. HELMS I 1,862,115

AUTOMATIC COUPLING MECHANISM FOR SEMITRAILERS Filed May 31, 1930 5 Sheets-Sheet 5 i I QBQQRRQQ.

Patented June 7, 19 32 UNITED-[STATES PATENT oFF-ICE- HARRY W. HELMS, F DETROIT, MICHIGAN, ASSIGNOR TO HIGH TWAY TRAILER COM- IPANY, OF EDGERTON, WISCONSIN, A CORPORATION'OF WISCONSIN AUTOMATIC COUPLING MECHANISM FOR SEMITRAILERS Application flied May 81, 1930. Serial No'. 457,779.

This invention relates to a combined vehicle unit comprising a tractor and a semi- 'trailer adaptedto be coupledtogether for conjoint operation; and more particularly the present invention relates to semi-trailers of the type having load supporting means arranged for temporarily supporting the forward end of the trailer when itis disconnected from the tractor, and adapted to be automatically raised out of operative position by the relative movement of the vehicle units during the coupling operation.

The main object of the present invention I resides in the provision of means that is sub stantially automatic for effecting positive and speedy coupling and uncoupling of the vehicle units in response to their relative movements during these respective operations. Another object is toprovide safety check means for positively precluding rais-- ing of the temporary support of the trailer during coupling operation until it is assured that the tractor and trailer units are positively locked together in coupling relation. Other objects and advantages will be apparent as the description proceeds, taken in connection with the accompanying drawings, in

which a Figure 1 is a side elevation of a combined vehicle unit emb0dying the present invention; with the forward end ofthe tractor broken away, showing the rear end thereof in supporting relation under the front end of the trailer.

Figure 2 is a fragmentary enlarged longitudinal sectional view, with different portions of the section taken in staggered relation, showing the tractor and trailer fifth wheel members in proper registration ready for completing the coupling action.

Figure 3 is a sectional view somewhat similar to Figure 2 showing a possible misalignment of the tractor and trailer; the lower fifth wheel member on the tractor being shown inclining to one side of the tractor. Figure 4 is a transverse sectional view taken substantially as indicated at line, 4-4, on Figure 3. Figure 5 is a fragmentary longitudinal sectional view showing the tractor and trailer coupled together, with the auxiliary frame telescoped into the trailer main frame.

Figure 6 is a front end view of the trailer with the tractor coupled thereto, with portions broken away and in section to show details of construction; I Figure 7 is a fragmentary plan view of the front end of the trailer showing the auxiliary Irame telescoped in the main frame and with v parts broken away and shown in section to illustrate details of construction.

Figure 8 is a view similar to Figure? with parts in section taken just below the upper edge of the auxiliary frame, as indicated at line -8 8 on Figure 5.

Figure 9 is a fragmentary plan view of the rear end of theauxiliary frame and the main frame showing spring means for cushioning the impact of the auxiliary frame.

' Figure is an enlarged axial sectional view through the king pin, its sleeve and the Figure 13 is a plan view of the lower fifth wheel member on the tractor.

The present invention represents certain refinements and improvements in construction and operation in combined trailer units of the type disclosed in my co-pending Pat- 1 outs Nos. 1,783,087 issued November 25, 1930,

and 1,785,697 issued December 6, 1930.

Combined vehicles of this character are preferably made detachable to speed up and efiect economy in handling merchandise,

since one tractor vehicle ordinarily is capable of use in hauling a number of trailers alternately from place to place; one or more of the trailers remaining at the loadlng point durthe tractor and trailer units be constructed and arranged so that the coupling and uncoupling operations may be effected substantially automatically and positively with the utmost degree of safety to insure against injury to attendants or to the vehicle and its merchandise.

Referring now'iu detail to the drawings, the semi-trailer is shown provided with a main frame, 10, having supporting wheels, 11, at the rear end thereof, and the tractor which is shown fragmentarily and diagrammatically .is provided with a chassis frame, 12, partially supported on the rear wheels indicated at 13. To permit articulation of the tractor and trailer units in use for turning one vehicle with respect to the other when they are coupled there isherein shown a connection which comprises an upper fifth wheel member, l4,which is rigidly secured to the under side or bottom of a rectangular auxiliary frame, 15, which is slidably supported by and adapted to be telescoped into and out of the forward end of the main frame, 10, into coupling and uncouplingpositions respectively,--and a co-operating lower fifth wheel member, 16, mounted for tilting foreand-aft about a transverse horizontally dis posed shaft, 17, journaled in bearings, 18, on the rear end of the tractor chassis, 12. It may be understood that this lower fifth wheel member is so designed that it normally tends to assume a definite rearwardly tilted position substantially as shown in Figure 2 of the drawings.

Rigidly secured to the rear end of the auxiliary frame, 15, are a pair of transversely spaced supporting legs, 20, at the lower ends of which are journaled ground engaging wheels, 21, adapted to be automatically raised and lowered in response to the telescopic movement of the auxiliary frame and the main frame during coupling and uncoupling operations respectively. For simplicity and economy the auxiliary frame is preferably made up of structural members, and as herein shown includes a pair of side members in the nature of structural channels, 15, arranged with their flanges outturned so as to provide longitudinal guide tracks for engaging the rollers, 23. disposed at opposite sides of the auxiliary frame and mounted adjacent the forward end of the main frame by means of which the auxiliary frame is supported throughout its range of telescopic movement. These rollers are preferably journaled on studs, 24, which in turn are rigidly secured in brackets, 25, firmly sei cured to the front end of the trailer main frame, 10. It will be apparent that this arrangement of the supporting rollers is such as to afford substantially free and unhindered telescopic movement of the auxiliary frame. The auxiliary frame when extended forwardly of the trailer main frame is adapted to assume an upwardly inclined position, as seen in Figure 2, by virtue of its rear end being caused to travel downwardly under control of rollers, 27, journaled on the rear end of the auxiliary frame, for travel in downwardly inclined guide tracks, 28, which are rigidly secured to the trailer main frame at opposite sides of the auxiliary frame. Thus as the auxiliary frame is moved forwardly with respect to the trailer its path of movement is positively controlled by the rollers, 27, traversing the guide tracks, 28, while the rollers, 23, at the forward end of the main frame serve to provide a pivot or shifting fulcrum about which said auxiliary frame tilts to an upwardly inclined position. It is to be understood that when the auxiliary frame has-moved to said forwardly inclined position, the ground-engaging wheels, 21, have been simultaneously and positively lowered into operative position for temporarily supporting the front end of the trailer. The lower end of the guide track, 28, is so formed as to rovide a stop surface, 28 for the rollers, 2?, for positively limiting the extension of the auxiliary frame with respect to the trailer frame.

It is to be understood that while the trailer is uncoupled from the tractor the brakes of the trailer preferably remain set, but are automatically released upon completion of the coupling operation as shown and described in detail in my eo-pending Patent No. 1,783,087 issued November 25, 1930. Preparatory to uncoupling of the vehicle units the trailer brakes are applied, and to insure safety I prefer to set the brakes manually. For this purpose I provide a convenient hand lever, 30, pivoted at 31 to the front end of the trailer main frame and pivotally connected at 32 .to an operating rod, 33. It may be understood that the arrangement of the brake linkage is such that when the brakes are released the lever, 30, is normally disposed in substantially vertical relation as seen in Figure 1 and when the brakes are in applied position the lever, 30, is moved to a forwardly inclined positionas seen in Fig. 2.

' When the auxiliary frame is telescoped into the main frame it is locked therein by a pair of transversely spaced latching devices,

35, secured to the upright face of. a framing member, 36, which extends across the front end of the trailer main frame. These latch devices each include a vertically movable dog, 37 normally urged downward by a spring, '38, so as to project forwardly of and substantially engage the wear strip, 15*, extending across the forward end of the auxiliary frame. These dogs areeach provided with a laterally extending pin, 39, projecting through aslot, 35 in the latch housing in position to be engaged by fingers, 40, rigidly linkage,

secured on a rock shaft, 41, iournaled in said latching devices. Mounted on the end of this rock shaft, 41, adjacent the hand lever, 30, is a cam finger, 43, whose under side is provided with a cam surfa'ce, normall disposed in vertical position 'as seen in Figure 5, when the auxiliary frame is locked in the main frame. Said cam surface is adapted to be engaged by a laterally offset camming projection, 44, on said brake lever, 30, so that when said hand lever-is swung forwardly the projection, 44, a'cts camwise on said finger, swinging it in an upward direction, thereby turning the shaft, 41, so that the fingers, 40, by their engagement with the pins, 39, will raise the latch dogs, 37, releasing the auxiliary frame to permit the latter to be drawn outwardly from the end of the trailer main frame. It may be brake operating lever, 30, is swung forwardly into position for setting the brakes, it will be held in such position by any suitable detent device (not shown) associated with the brake and the locking dogs will be held clear of the auxiliary frame by the camming projection, 44, engaging the cam finger, 43, in a manner to prevent any pressure exerted through the finger, 38, of the latch devices tending'to swing the brake operating lever to upright position and release the locking do s.

sleeve, 50, is rigidly secured to and projects' downwardly from the under side of the upper fifth wheel member, 14, and is formed at its lower edge with a flange, 51, adapted to engage in an undercut groove, 52, formed in the closed end of a rearwardl open .V-shaped slot, 16*, formed in the lower fifth wheel member, 16. This V- hape-d jslot terminatesin a semi-circular bearing, 53, which receives the sleeve, 50, and insures centering of the fifth wheel members of the two vehicle units when the tractor is backed toward the trailer in coupling operation. The bottom surface of the part, 16, at a point concentric with the semi-circular bearing, 53, is provided with a tapered aperture, 54, with which co-operates the tapered end of an axially movable king pin, 55, which is telescopically carried in said sleeve, 50. The lower fifth wheel member, 16, is preferablya cast member and is provided with' a seat for a plate, 56, which-is formed with a rearwardly inclined ortion, 57, as seen in Figure 1, so as to facllitate guiding the sleeve into the V slot during the coupling operation of the vehicle units thus, the sleeve, 50, when it engages the inclined portion, 57, of the lower fifth wheel member will be directed to the semi-circular bearing, 53, in the majority of cases, and evenwhen the tractor andtrailer units are slightly misaligned vertically so that the forward end of the trailer is supported a little lower than normally with respect to the lower fifth wheel of the tractor. The flange,

the undercut groove,

understood that when the 51, of the sleeve when engaged in I 2 ticalseparation of the fifth wheel members of the respective vehicle units, and when the king pin, 55, is projected downwardlyfrom the sleeve so as toengage in the tapered seat, 54, in the lower fifth wheel member, by means will preclude ver- 1 which willhereinafter be described, the fifth wheel members will zontal vseparation.

Carried at the front end of the main frame and disposed wholly within the auxiliary frame, is a horizontal cross shaft, 60, supported at its ends in a bracket, 61 which in turn is secured to the under side of the angle member, 36, which extends across the front of the main frame. Pivotally mounted on the upper surface ofthe upper fifth wheel member, within the auxiliary frame in .a bearing longitudinally extending operating lever, 65, of inverted U-sha ed cross section. This lever extends a su stantial portion of the length of the auxiliary frame with its forwardmost end engaging beneath the cross shaft, 60, as may be seen in Figure 5 of the drawings. Pivoted approximately midway of the length of said lever, at 66, is the king P a sleeve, 50, under the control of said lever. The lever has a portion extending rearwardly beyond its fulcrum inclining upwardly to provide a cam surface, 67, and to the extreme rear end of said portion there are pivotally connected at 68, a pair of ;locking members, 69, which are formed with hooked ends, 70, normally disposed below the upper surface of the lever, 65. These hooked ends are rockable upwardly about the pivot, 68, by virtue of projections, 71, on the under sides of said locking members which rest upon the upper surface of the upper fifth wheel member, 15, so that as the forward end of said lever, 65, is swung upwardly about its fulcrum. These pro ections, 71, serve as fulcrums for the locking members causing their be locked against horihook portions, 7 0, to swing upwardly above the surface of the operating lever, as may be seen in Figure 2 of the drawings. It will.

be apparent that substantially the entire upper surface of the operating lever, 65, is in effect a camming surface which is 'slidably engaged by the undersurface of the cross shaft, 60, and that when the auxiliary frame ing under the shaft, 60, .the king pin will remain extended. in its sleeve until the inclined cam surface, 67, is engaged by said shaft, which will then cause swinging of said lever upwardly about its fulcrum. 'This movement will withdraw the king pin into thesleeve, and simultaneously cause rocking 'bf thelocking members so that their hook ortions, 70, will be projected up above the ever, directly in front of the shat, 60. Thus return movement of the auxiliary frame into bracket, 64, is a centrally located which is axially movable in its rigid .is drawn out forwardly with'thelever sli'dthe main frame is normally prevented by rea-' son of the hooks, 70, engaging said transverse shaft, 60.

In couplin the tractor and trailer, the tractor is backed toward the trailer, and by virtue of the fact that both fifth wheel members are co-operatively tilted the fifth wheels are quickly brought into registration with the sleeve, 50, following the V-groove to the swivel bearing, 53, of the lower fifth wheel; and as may be seen in Figure 2, when the auxiliary frame has been shifted slightly rearwardly so that the inclined cam surface, 67, of the lever has been freed from control of the shaft, (30, and the operating lever is ready to swing downwardly about its fulcrum, and drop the king pin, 55, through the sleeve, into its seat, 54, in the lower fifth wheel member. As the auxiliary frame conprises a latch member, 75,

tinues rearward movement from the position shown in Figure 2, the shaft, 60, acting camwise against the forward part of the operating lever, tends to force it downwardly, for moving the king pin into locking position. However, unless the seat, 54, is aligned with the king pin such action is prevented, and the rearward movement of the auxiliary frame is checked by the hooks, 70, engaging the shaft, 60. lVhen the king pin is registered with its seat, the cam action of the Shaft, 60, on lever, 65, will force the king pin into its seat and simultaneously lower the.

hooks below the shaft, 60, permitting the auxiliary frame to be .telescoped into the main frame. j

' Since the telescoping of the auxiliary frame into the main frame serves to raise the supports, 20, and Wheels, 21, from trailer-supporting position to their elevated, inoperative position, it is important to insure that the tractor and trailer are-properly and positively coupled before this is done. Therefore, I provide safety means which positively precludes backing of the auxiliary frame into the main frame until the fifth-wheel elements of the trailer and tractor units have been securely locked together. This means compivotally mounted at 76 in a slot, 77, of the king member is formed with a portion, 75*,which is adapted to be projected radially inward for engaging a stop shoulder, 78, of the king pin and supporting the same in upwardly retracted position in the sleeve, as shown in Figure 10. The king pin preferably has its lower portion below said shoulder, 78, cutaway to insure positiveness of engagement of the latch portion, 7 5", with said shoulder. The latch member is alsdprovided with .a tail portion, 75", which is dimensioned so that when the latch portion, 75, is in operative engagement with the shoulder of the king pin, said tail portion, 75 projects laterally beyond the outer wall of the sleeve, and said the lower fifth pin sleeve, 50, as seen in Fig. 11 of the drawings; said latch latch member is bearing surface, 53, of the lower fifth wheel member above the undercut groove, 52, into which the flange, 51, is received when the parts are properly positioned for coupling.

It will now be apparent that by reason of the shape of this latch member, it will always retain the king pin in its upwardly retracted position until the projection, 7 5*, is engaged so as to swing the latch portion, 7 5*, out of supporting relation with the shoulder, 78, of the king pin. However, it will be manifest that because the flange, 51, of the sleeve projects laterally beyond the tail portion, 75, the latter'cannot be engaged byvany'simple upright surface, butonly one where there isan undercut to accommodate the flange, 51. Accordingly when the tractor is moved toward the trailer during the coupling operation the sleeve, 50, will ride up the incline of wheel member and be directed toward the bearing, 53, by the converging as the sleeve engages in said bearing, 53, with its flange in the undercut groove, 52, the latch tail, 7 5 will be engaged by the curved bearing surface, 53, swinging said latch about its pivot, 76, so that the latch portion, 75*,will then move free of the shoulder, 78, to release the king pin,55. l/Vhen the king pin is thus aligned with the opening, 54, and thenonly, is the operating lever, 65, permitted to swing downwardly by the cam action of the shaft, 60, to move the king pin to its seat; and as above mentioned, until said lever, 65, is permitted to swingdownwardly, thehook portions, 70, will be disposed in a position to en unter the shaft, 60, and thereby preclude a rther rearward movement of theauxframe. This latching device by means of which the king pin is positively locked within the sleeve until it is aligned over its seat in the lower fifth wheel member, thus adds considerably to the safety of the vehicle. To illustrate its utility, Figures 3 and 4 show portions of the coupling elements in a possibly exaggerated relation, wherein the tractor element is assumed to be supported on irregular ground so that its fifth wheel member is canted laterally to one side. In such yieldingly held in such posi- I tion by a flat spring, 79, secured to the sleeve agin the lower surface of the slot, because.

I the fi h wheel members are supported only at a small area atone side of the center.

. main frame. It will be manifest that if telescopic movement of the auxiliary frame were permitted without coupling of the vehicle,

' the forward end of the trailer would be left on the tractor and would be and pitch forward to the ground as soon as the tractor moved forward and" becamev disengaged by reason of the insupported only likely to slip off complete coupling. But such accidents are prevented by the safety latch, 7 5.

To cushion the impact of the auxiliary frame when it is telescoped into the main frame of the trailer, and to relieve strain. on the various elements, I preferably provide means for absorbing the shock incident to said telescopic movement, which consists of a pair of transversely spaced coil springs, 81,

. secured to a cross member, 10, of-the vehicle main frame, with the springs arranged to encounter the rear end of the auxiliary frame, as may be seen in Figure 9 of the drawings. The vehicle construction embodying this invention is relatively simple in design and is substantially automatic, and is positive in operation; thus insuring anunusually high degree of safety while at the same time being of rugged construction, capable of withstanding the usual rough abuse accorded such vehicles.

AlthoughI have shown and described one particular embodiment of my'invention it will be understood that it is capable of vari- 0115 changes and modifications without departing from the spirit and scope thereof. a

I do not therefore, wish to be understood as limiting mysef to the particular specific embodiment herein shown, except as indicated by the claims.

y I claim:

1. In combination, a'tractor, a semi-trailer having a main frame, a connection including an upper the trailer and a lower fifth wheel member mounted on thetractor, said lower member havin a rearwardly open V-shaped' slot terminating adjacent the center of said lower. member in a swivel bearing having an undercut groove, and a. flanged swivel member carried onthe upper fifth wheel member and adapted to be guided in said V-slot into the swivel bearing with its flange portion engaged in said undercut groove for preventing vertical separation of said fifth wheelmembers. I

2. In a combined vehicle unit comprising a by the upper operations for fifth wheel member carried on' tractorand a semi-trailer, a fifth wheel swivelly supporting one end of the trailer on the tractor when coupled thereto, said fifth wheel comprising a lower member carried on the tractor and an upper member supported by the trailer, said upper member being mov able relative to the trailer during coupling ter position when the vehicle units are uncoupled.

3. In a combined vehicle unit comprising a tractor and a semi-trailer, a fifth wheel swivelly supporting one end of the trailer on the tractor when coupled thereto, said fifth wheel comprising a lower member carried on the tractor and an upper member supported by'the trailer, said upper member being movable reiative to the trailer during coupling and uncoupling operation, a king pin carried fifth wheel member and axially movable thereon, means responsiveto said relative movement of the upper fifth wheel member during coupling and uncoupling respectively moving said king pin in axial direction into or out of operative engagement with the lower fifth wheel member, and means for automatically encoupled, and adapted to release said king pin for permitting said first mentioned means to move it to operative position when saidvehicle units are moved into coupling position.

4. In a combined vehicle unit comprising av tractor and a semi-trailer, a fifth wheel swivelly supporting one end of the trailer on the tractor when coupled thereto, said fifth wheel comprising the tractor'and an upper member supported by the trailer, said upper member being movable relative to the trailer during coupling and uncoupling ope'ration, a sleeve fixedly secured to said upper fifth wheel member and adapted to be swivelly engaged in the closed end'of a rearwardly open slot in the lower fifth wheel member, said sleeve havlng a flange adapted to engage in groove in the swivel bearing for preventing vertical separation of the fifth wheel members, a king pin axially movable in said sleeve and a apted to be moved into engagement with the lower fifth wheel member or locking-said fifth wheel members against hormeans responsive to the movement of the upper an under-cut.

a-lower member carried on for holding the same in inoperative position when said vehicle units are uncoupled, and

having a portion adapted to be extended beyond the wall of the sleeve for encountering the closed end of the slot in the lower fifth wheel member, during coupling operation, or swinging said latch out of engagement with the shoulder for permitting said means to move the king pin into operative engagement with the lower fifth wheel member.

5. In the construction defined in claim 4, spring means normally urging the latch into position for engaging the king pin.

6. In the construction defined in claim 4, said latch member being pivotally mounted in a slot of the sleeve, and being dimensioned to substantially lie within the cross sectional area of the sleeve when the leased.

king pin is re-v 7. In a combined vehicle unit comprising a tractor and a semi-trailer having a main frame, an auxiliary frame carried and telescopically associated with the main frame, a two-part swivel including an upper fifth wheel member carried on the auxiliary frame, and a lower fifth wheel member carried on the tractor, said auxiliary frame being adapted for forward extension during ungoupling of the vehicle units, and adapted to the trailer during coupling operation, and

and engageable with the other for cushioning the impact of the auxiliary frame when'the same. is telescoped into the main frame.

8. tractor and a semi-trailer having a main frame, an auxiliary frame carried and tele- Scopically associated with the main frame, a two-part swivel including an upper fifth wheel member carried on the auxiliary frame, and a lower fifth wheel member carried on the tractor, said auxiliary frame being adapted for forward extension during uncoupling of the vehicle units, and adapted to be returned by backing the tractor toward the trailer during. coupling operation, and spring means carried on the main frame and arranged for engaging the rear end of the auxiliary frame for cushioning the impact of the same when frame.

9. In a combined vehicle unit comprising a tractor and a semi-trailer having a main frame, an auxiliary'frame carried by and telescopically associated with the I main rame, a two-part swivel including an upper fifth wheel member carried on the auxiliary frame, and a lower fifth wheel member carried on the tractor, said auxiliary frame being adapted for forward extension during uncoupling of the vehicle units, and adaptede. returned by backing the tractor toward In a combined vehicle unit comprisinga it is telescoped into the main.

mounted on said shaft and arranged for 011- gaging said dog and moving it out of operative position, the main frame below said shaft and normally disposed in substantially vertical position, and means responsive to forward movement of said leveradapted for turning the shaft for moving the dog out of locking position with the auxiliary frame.

10. In the construction defined in claim 9, said means including a cam finger on the-rock shaft, and a cooperating part on said lever adapted to act cam-wise against said finger for rocking the shaft.

11. In a combined vehicle unit comprising a tractor and a semi-trailer having a main frame, an auxiliary frame carried by and longitudinally slidable relative to the main frame, an upper fifth wheel member carried on the auxiliary frame, and a lower fifth wheel member carried on the tractor, said auxiliary frame being adapted to be forward ly extended relative to the trailer during uncoupling of the vehicle units, and adapted to frame, and yieldingly urged into an operating lever pivoted to including a vertically movable dogbe returned by backing the tractor toward the 1 ing said fifth wheel members together dur ing uncoupling and coupling operations respectively; said means ncluding a longitudinally extending operating lever fulcrumed adJacGnt its rear end on the auxiliary frame and having its upper surface serving as a cam, a king pin pivotallyconnected to said lever, a transverse cross member rigidly secured to the main frame and disposed entirely within the auxiliary frame for cooperating with the cam surface of said lever for swinging it about its fulcrum and thereby moving the king pin into or out of en agement with its seat in the lower fifth Wheel member, and a hook member pivoted to the lever rearwardly of its fulcrum and adapted when said auxiliary frame is extended, to be moved upwardly and in front of the cross member by the action of said cross member on the lever and adapted to encounter the cross member and preclude return movement of the auxiliary frame unless said lever is permit-, ted to move downwardly and project the king pin into its seat in the lower fifth wheel mem- 12. In a semi-trailer, a main frame, an auxiliary frame carried by and longitudinally movable relative to the main frame, and

a tractor carried on said auxiliary frame,

coupling means for connecting the trailer sai frame being adapted for forward movement relative to the main frame during uncoupling of the tractor and trailer, and adapted to be returned by the backing of the tractor toward the trailer in the coupling operation; a pair of axially aligned stub shafts IDOUHtGdtLdjEI- cent the front end of the main frame at opposite sides of the auxiliary frame, rollers on said shafts engageable with the auxiliary frame, said auxiliary frame having side members consisting of channels arranged with outturned flanges for engaging said rollers throughout the rangeof movement of said auxiliary frame, together with means associated with the rear end of the auxiliary frame for controlling the movement of said frame over said rollers.

- HARRY W. HELMS. 

